Folded or crumpled proppants with increased material strength for hydraulic fracturing, gravel packing and frac packing

ABSTRACT

Relatively low strength and/or relatively low density, but ductile materials may be folded or crumpled and finely divided to give proppants for introduction into hydraulic fractures, where the folded or crumpled structure of the proppants gives relatively increased strength relative to the relatively low strength and/or relatively low density of the materials. Materials not previously considered suitable for proppants may be considered when structure or configured in this manner. Similarly to the case where crumpled paper within a cardboard box keeps it from collapsing, the folded or crumpled material spontaneously develops structural rigidity at relatively low volume fractions without a specific externally imposed design. The folded or crumpled proppants may also be used alone or together with conventional proppants for sand control in gravel packs or frac packs.

TECHNICAL FIELD

The invention relates to methods of making and compositions forproppants for introduction into the hydraulic fractures of asubterranean formation and sand control methods, such as gravel packingand frac pack and more particularly relates to methods of making andcompositions for proppants which permit the proppants to be made ofrelatively low-strength and/or low-density materials but which may stillgive a proppant of comparable strength to conventional proppants.

TECHNICAL BACKGROUND

Hydraulic fracturing is a common stimulation technique used to enhancethe production of hydrocarbon fluids from subterranean formations. In atypical hydraulic fracturing treatment, fracturing treatment fluidcontaining a solid proppant material is injected into the formation at apressure sufficiently high enough to cause the formation to fracture orcause enlargement of natural fractures already present in the reservoir.The fracturing fluid that contains the proppant or propping agenttypically has its viscosity increased by a gelling agent such as apolymer, which may be uncrosslinked (linear) or crosslinked, and/or aviscoelastic surfactant. During a typical fracturing treatment, proppingagents or proppant materials are deposited in a fracture, where theyremain after the treatment is completed. After deposition, the proppantmaterials serve to hold the fracture open, thereby enhancing the abilityof fluids to migrate from the formation to the well bore through thefracture. Because fractured well productivity depends on the ability ofa fracture to conduct fluids from a formation to a wellbore, fractureconductivity is an important parameter in determining the degree ofsuccess of a hydraulic fracturing treatment and the choice of proppantmay be critical to the success of stimulation.

Because the proppants must hold the fracture open, traditional proppantsare made from very strong and/or crush-resistant materials. Suitabletraditional proppants include, but are not necessarily limited to, whitesand, brown sand, ceramic beads, glass beads, bauxite grains, sinteredbauxite, sized calcium carbonate, walnut shell fragments, aluminumpellets, nylon pellets, nuts shells, gravel, resinous particles,alumina, minerals, polymeric particles, and combinations thereof. Itwill be appreciated that since relatively large amounts of proppants areoften used in a proppant stage that it is important to consider ways ofreducing the cost of proppants.

Proppant-like deformable particles have also been used in conjunctionwith proppants for various purposes, for instance, in order to minimizeproppant flow back problems.

Proppant has also been used for gravel pack operations. Gravel packingis a sand-control method employed to prevent the production of formationsand. Gravel packing treatments are used to reduce the migration ofunconsolidated formation particulates into the wellbore. Typically,gravel pack operations involve placing a gravel pack screen in thewellbore and packing the surrounding annulus between the screen and thewellbore with gravel designed to prevent the passage of formation sandsthrough the pack. The gravel pack screen is generally a type of filterassembly used to support and retain the gravel placed during the gravelpack operation. Particulates known in the art as gravel are carried to awellbore by a hydrocarbon- or aqueous-based carrier fluid, includingviscosified or brine-based systems. The carrier fluid leaks off into thesubterranean zone and/or is returned to the surface while theparticulates are left in the zone. The resultant gravel pack acts as afilter to separate formation sands from produced fluids while permittingthe produced fluids to flow into the wellbore.

In some situations the processes of hydraulic fracturing and gravelpacking are combined into a single treatment to provide stimulatedproduction and an annular gravel pack to reduce formation sandproduction. Such treatments are often referred to as “frac pack”operations. In some cases, the treatments are completed with a gravelpack screen assembly in place, and the hydraulic fracturing treatmentbeing pumped through the annular space between the casing and screen. Insuch a situation, the hydraulic fracturing treatment usually ends in ascreen out condition creating an annular gravel pack between the screenand casing. This allows both the hydraulic fracturing treatment andgravel pack to be placed in a single operation.

It would be desirable to provide a method and material for proppantsthat give choices of less expensive and/or alternate materials which maynevertheless be suitable for proppants. It would also be desirable toprovide proppants of relatively low density and/or low specific gravity.

SUMMARY

There is provided in one non-limiting embodiment a proppant comprisingat least one crumpled layer having outer perimeter defining a proppantvolume, and at least one interstice within the proppant volume adjacentthe layer.

There is additionally provided in one non-restrictive version, a methodof making a proppant comprising providing a layer, and not necessarilyin this order: crumpling the layer and finely dividing the layer. Themethod produces a proppant comprising at least one crumpled layer havingouter perimeter defining a proppant volume, and at least one intersticewithin the proppant volume adjacent the layer.

Further there is provided in a different non-restrictive embodiment amethod of fracturing a subterranean formation comprising introducing aproppant stage into the subterranean formation, wherein the proppantstage comprises a carrier fluid and a proppant. The carrier fluid mayinclude, but not necessarily be limited to, brine, slickwater, anaqueous fluid gelled with a linear gel, an aqueous fluid gelled with acrosslinked gel, an aqueous fluid gelled with a viscoelastic surfactant,a fluid containing a gas (e.g. carbon dioxide and/or nitrogen), andmixtures thereof. The proppant comprises at least one crumpled layerhaving outer perimeter defining a proppant volume, and at least oneinterstice within the proppant volume adjacent the surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a relatively flat layer ofrelatively ductile proppant material;

FIG. 2 is a schematic illustration of the relatively flat layer ofrelatively ductile proppant material of FIG. 1 after it has beencrumpled;

FIG. 3 is a schematic illustration of a single proppant particle formedfrom a crumpled relatively ductile proppant material, formed into aparticle and placed within a fracture.

It will be appreciated that the various Figures are not necessarily toscale and that certain features have been exaggerated for clarity and donot necessarily limit the features of the invention.

DETAILED DESCRIPTION

Conventional materials used for propping open fractures created insubterranean formations during oilfield operations have inherently highstrength, but also usually have high density. In contrast, low-densityproppant is easier to transport into a fracture. It has been discoveredthat relatively low-strength (and low density) but ductile materials mayhave their strength increased through folding or crumpling the material,which provides added strength in three dimensions, similar to theprinciple of using crumpled paper to keep a box from collapsing duringshipping. This same principle should enable the use of materials neverconsidered previously for proppants because of their low inherentstrength. See, for instance, A. D. Cambou, et al., “Three-DimensionalStructure of a Sheet Crumpled into a Ball,” Proceedings of the NationalAcademy of Science, Vol. 108, No. 33, Aug. 23, 2011, pp. 1-5,incorporated herein by reference in its entirety.

Ultra lightweight proppants are easier to transport down a longhorizontal well section and deep into a fracture, but are more difficultto manufacture than natural sand, ceramic or bauxite proppants that canwithstand the closure stresses required to hold open the fracture. Mostconsiderations of new materials for ultra lightweight proppants consideronly materials with inherent high strength. The conventional thinking isthat porosity or voids within proppants particles will weaken thematerial. The proppants described herein are different. These proppantsrely on voids and porosity to maintain the material density as theductile material folds or crumples itself into a multi-walled structurethat exhibits 2 to 5 times the strength of a single layer of the samematerial. This ideally enables the use of materials previouslyconsidered too weak to support downhole closure stresses.

It is expected that the proppants described herein may be made in avariety of ways. In one non-limiting embodiment, the proppant materialis sprayed using an atomizer, including, but not necessarily limited to,a nebulizer or other device to form a thin layer from a fine mist,spray, fog or aerosol, which layer is then exposed to quick heating fordehydration thus crumpling the layer. The resulting granules are thencompacted, folded or crumpled to obtain the most benefits within theparameters described herein. Optionally, the resulting material may becoated with a resin. In another optional embodiment, the resultingmaterial may be sintered at high temperature. In order to keep theporosity high, the material may be put in a furnace at relatively hightemperature and then cooled very quickly. “High temperature” is definedherein as from about 800 to about 1500° C. If the layer is not flexibleenough then a polymer such as carboxymethyl cellulose (CMC), epoxy,guar, and the like could be added.

In another non-limiting embodiment, a very thin layer of material havinga relatively large area may be crumpled and or folded and then finelydivided by chopping, granulating, grinding, cutting, comminuting orother size reduction method. The very thin layer may be a bilayer (ormultiple layers) of two materials that expand or contract at differentrates when subjected to heating or cooling cycles, respectively, orboth, where the different rates cause the bilayer (or multiple layers)to fold, buckle or crumple. The sequence could also be reversed. Thatis, a very thin layer of material having a relatively large area may befinely divided by chopping, granulating, grinding, cutting or other sizereduction, and then the tiny pieces could be crumpled and or folded,such as by the techniques described herein, or additionally rolled,pressed, compacted or otherwise formed into relatively uniformly sizeparticles of roughly spherical shape. It will be appreciated, however,that shapes other than spheres may be suitable for the proppantsdescribed herein, including, but not necessarily limited to, beaded,cubic, bar-shaped, cylindrical, elongated, or a mixture thereof.

In a different non-restrictive version, the technology used to makehollow microcapsules, such as used in pharmaceutical and other agentdelivery, could be used to make hollow, tiny spheres, which would thenbe crumpled and/or folded to make the proppants. Unlike for some uses,the microcapsules would not necessarily have to be air tight—that is,they could have voids or holes—and it would not matter if the sphericallayer or shell was broken in the crumpling or folding. Indeed, the goalof making relatively perfect microcapsules for most such applicationswould not be needed to make the proppants described herein.

Indeed, what is important in all of these embodiments is tospontaneously create proppant particles that develop structural rigidityat very low volume fractions without externally imposed design, exceptfor forming the volume or outer dimensions of the proppants. Thisrigidity has been attributed to the formation of ridges with highbuckling strengths, again as in the case where crumpled paper keeps acardboard box from collapsing, protecting the contents of an objectedpacked with crumpled paper inside the box.

Suitable materials for the proppants herein include, but are notnecessarily limited to, ceramics, carbon materials, metals, polymers,and combinations thereof. Suitable ceramic materials include but are notnecessarily limited to, oxide-based ceramics, nitride-based ceramics,carbide-based ceramics, boride-based ceramics, silicide-based ceramics,or a combination thereof. In a non-limiting embodiment, the oxide-basedceramic may include, but is not necessarily limited to, silica (SiO₂),titania (TiO₂), aluminum oxide, boron oxide, potassium oxide, zirconiumoxide, magnesium oxide, calcium oxide, lithium oxide, phosphorous oxide,and/or titanium oxide, or a combination thereof. The oxide-basedceramic, nitride-based ceramic, carbide-based ceramic, boride-basedceramic, or silicide-based ceramic may contain a nonmetal (e.g., oxygen,nitrogen, boron, carbon, or silicon, and the like), metal (e.g.,aluminum, lead, bismuth, and the like), transition metal (e.g., niobium,tungsten, titanium, zirconium, hafnium, yttrium, and the like), alkalimetal (e.g., lithium, potassium, and the like), alkaline earth metal(e.g., calcium, magnesium, strontium, and the like), rare earth (e.g.,lanthanum, cerium, and the like), or halogen (e.g., fluorine, chlorine,and the like). Exemplary ceramics include, but are not necessarilylimited to, zirconia, stabilized zirconia, mullite, zirconia toughenedalumina, spinel, aluminosilicates (e.g., mullite, cordierite),perovskite, silicon carbide, silicon nitride, titanium carbide, titaniumnitride, aluminum carbide, aluminum nitride, zirconium carbide,zirconium nitride, iron carbide, aluminum oxynitride, silicon aluminumoxynitride, aluminum titanate, tungsten carbide, tungsten nitride,steatite, and the like, or a combination thereof.

Suitable carbon materials include, but are not necessarily limited to,carbon nanotubes, graphene and its oxide, graphite, and combinationsthereof. Suitable metals include, but are not necessarily limited to,titanium, aluminum, and alloys thereof and combinations thereof.Suitable polymer include, but are not necessarily limited to,carboxymethyl cellulose (CMC), polyethylene terephthalate, polyimides,polypropylene, polyethylene, polycarbonate, polyurethane, andcombinations thereof. In short, any material that can form a sheet orlayer, and which will crumple under dehydration and/or be formed byfolding or other force and be sufficiently strong after being formedinto crumpled particles will work.

As schematically shown in FIG. 1, the sheet or layer 10 describedpreviously may have a thickness, t, between about 1 mm independently toabout 5 microns; alternatively from about 30 microns independently toabout 10 microns. As used herein with respect to a range, the term“independently” means that any lower threshold given may be combinedwith any upper threshold given to provide a suitable alternative range.It will be appreciated that the layer, sheet or shell 10 need notnecessarily be perfectly smooth, or even necessarily uniformly thick.Layer or sheet 10 may be textured in one or more ways including, but notnecessarily limited to, ridged, dimpled, scored, stippled, waved,crosshatched, and the like and combinations of these as long suchtexture does not interfere with the goal of providing crumpled or foldedproppants of suitable strength. Indeed, it is expected that some ofthese textures will enhance the strength of the folded or crumpledproppants.

Schematically illustrated in FIG. 2 is a folded or crumpled layer orsheet 12, such as what may result from crumpling or folding entire sheetor layer 10 of FIG. 1. When crumpled layer or sheet 12 is finely dividedand optionally shaped, a proppant particle 14 results as schematicallyillustrated in FIG. 3. Proppant particle 14 includes at least onecrumpled layer 16 having outer perimeter defining a proppant volume 18,and at least one interstice 20 within the proppant volume 18 adjacentthe layer 16. It will be appreciated that even if a single sheet orlayer 10 is used to make proppant particles 14 that in the process ofcomminuting or reducing the size and shape of the single sheet or layer10 to give the proppant particles 14 that various of the proppantparticles 14 may in fact be composed of two or more layers 16 that arecompressed together.

It will be appreciated that although proppant particles 14 will likelydefine or configured as a roughly spherical shape or volume 18, such asthat shown in FIG. 3, that as with conventional proppants, other shapesmay be acceptable or desired. Such suitable shapes may include, but arenot necessarily limited to, spheres, spheroid, ellipsoid, beaded, cubic,bar-shaped, cylindrical, or combinations or mixtures thereof. As is wellknown spherical or spheroid shapes are the most common shapes in theindustry, and the industry has had long experience with these shapes, soit should be expected that spheroid shapes would be accepted andcommonly used. However, in some non-limiting instances, such as partialmonolayer applications, other shapes besides spheres may be acceptable.In the case of a generally spherically shaped proppant particle 14 suchas that shown in FIG. 3, it will be appreciated that the volume 18 maybe calculated from the diameter, d, using the formula V=(4/3)πr³, whereV is the volume and r is the radius, which of course is simply d/2.

It will further be appreciated that the proppant particles 14 willlikely have a plurality of interstices 20 adjacent to the layers 16.Again, it will be appreciated that the crumpled state of the proppantparticles 14 spontaneously develops structural rigidity at very lowvolume fractions without externally imposed design, except for formingthe volume 18 or outer dimensions of the proppants 14. This rigidity hasbeen attributed to the formation of ridges with high buckling strengths,again as in the case where crumpled paper keeps a cardboard box fromcollapsing, protecting the contents of an objected packed with crumpledpaper inside the box, although in this case, the proppants 14 resist theupper fracture face 22 from collapsing onto the lower fracture face 24,as seen in FIG. 3. Upper fracture face 22 and lower fracture face 24define two boundaries of fracture 26. The folded and crumpled structuresof proppant particles 14 permit the use of relative low-strength and/orrelatively low-density, but ductile materials to be used, yet theproppant particles 14 may have the equivalent strength of conventionalproppants. In one non-limiting embodiment the proppant particles 14 maybe able to withstand pressures ranging from about 1,000 independently toabout 10,000 psi (about 6.9 to about 69 MPa); alternatively from about2000 independently to about 5000 psi (about 13.8 to about 34.5 MPa). Itis thus appreciated that the “strength” discussed herein is compressivestrength.

Proppant particles 14 may have an average particle size of from about125 independently to about 1700 microns. Common ranges for proppant andfines control methods including frac packing and gravel packing include,but are not necessarily limited to, 12/18 mesh (about 1680 independentlyto about 1000 microns); 20/40 mesh (about 841 independently to about 400microns); 30/50 mesh (about 595 independently to about 297 microns);40/70 mesh (about 400 independently to about 210 microns); 100 mesh (149microns) and in some instances below about 100 mesh (149 microns) asneeded for certain applications.

It should be understood that the folded or crumpled proppants describedherein will find a wide variety of uses including, but not necessarilylimited to, proppant packs, and in sand control structures including,but not necessarily limited to, gravel packs, frac packs andcombinations thereof. Such packs may include only the folded or crumpledproppants, or may include a mixture or combination of folded or crumpledproppants along with conventional, solid proppants. These packs andstructures will inhibit, prevent or otherwise control the unwantedproduction of sand.

It will be appreciated that due to the relatively large number ofinterstices 20 and the total volume of interstices 20 in a volume 18 ofthe proppant particles 10 that the density of the proppant particles 10will be relatively low, in a non-limiting instance below about 2.4 g/cc,and alternatively below about 2 g/cc. The interstices 20 will also aidin the proppants 10 having greater porosity than conventional proppantsthat are solid, thereby increasing conductivity through the proppantpack. It should also be appreciated that the porosity or proportion ofvoids within proppants 14 will depend on the exact materials and exactprocesses used to make them. Traditional or conventional proppants aredefined herein in one non-limiting embodiment as proppants that aresolid, and in another non-restrictive version as solid proppants havingan absence of an interstice.

In another non-limiting embodiment, the proppant particles herein may bea relatively lightweight or substantially neutrally buoyant particulatematerial or a mixture thereof. By “relatively lightweight” it is meantthat the solid particulate has an apparent specific gravity (ASG) ordensity which is less than or equal to 2.45, including those ultralightweight materials having an ASG less than or equal to 2.25,alternatively less than or equal to 2.0, in a different non-limitingembodiment less than or equal to 1.75, and in another non-restrictiveversion less than or equal to 1.25 and often less than or equal to 1.05.

It is expected that the same placement method known to be used in theart for ultra lightweight (ULW) proppants may be used for the placementof the proppants described herein into the subterranean formation. Forexample, a proppant stage may be introduced into a subterraneanformation using a carrier fluid and the proppants described herein,where suitable carrier fluids include, but are not necessarily limitedto, brine, slickwater, an aqueous fluid gelled with a linear gel, anaqueous fluid gelled with a crosslinked gel, an aqueous fluid gelledwith a viscoelastic surfactant, and mixtures thereof, and other types ofdelivery systems including but not necessarily limited to those withusing a gas, including, but not necessarily limited to nitrogen and/orcarbon dioxide (CO₂). Suitable proppant loadings in the proppantplacement methods herein include, but are not necessarily limited toabout 0.1 independently to about 12 lbs per gallon (about 0.01independently to about 1.4 kg/liter), alternatively from about 1independently to about 10 lbs per gallon (about 0.1 independently toabout 1.2 kg/liter).

It is also expected that in some non-limiting embodiments that theproppants described herein may be used to minimize proppant flow backproblems. Undesirable proppant flow back occurs when proppant is flowedback along with production fluids (e.g. oil and/or gas). If sufficientproppant flows back, then there may not be enough proppant within thefracture to hold the fracture open to increase permeability and improvefluid production. In one non-restrictive version, in a comparison ofotherwise identical methods of fracturing a subterranean formationforming a proppant pack within a fracture of the proppants describedherein and forming a proppant pack using solid proppants ofsubstantially the same shape as those of the proppants described herein,less proppant is flowed back using the proppants described herein thanwith the solid proppants. In another non-limiting embodiment, the amountof proppants flowed back is reduced from about 10 wt % or more proppantproduced to about 100 wt %, comparing the proppants to a methodotherwise identical except that the proppants are solids ofsubstantially the same shape.

It will also be appreciated that the folded or crumpled proppantsdescribed herein may be mixed with conventional or traditional proppantssuch as solid proppants. Such mixtures may be used in fracture proppantpacks for improved (reduced) proppant flowback control. In the instanceof proppant flowback control, it is anticipated that in somenon-limiting embodiments a mixture of shapes (e.g. spherical withelongated, cylindrical, cubic, beaded, bar-shaped and the like andmixtures thereof) and/or as well as types (e.g. folded or crumpledproppants mixed with conventional proppants) will be effective inreducing, inhibiting or preventing proppant flowback. Flowback controlwill depend to some extent upon the flexibility of the proppantmaterials used. In one non-limiting embodiment, it will be understoodthat the crumpled or folded proppants are relatively more deformablethan conventional solid proppants. In a further non-restrictive version,when the deformable crumpled or folded proppants are mixed withconventional solid proppants, the proportion of deformable crumpledproppants are less than about 25 wt % of the total amount of proppants,and alternatively less than about 15 wt % of the total mass ofproppants.

Additives, such as fillers, plasticizers, and rheology modifiers may beused in the proppant materials described herein in order to achievedesired economical, physical, and chemical properties of the proppantmaterials during the mixing of the chemical components and forming ofthe particles, and the field performance of the proppants.

Compatible fillers include, but are not necessarily limited to, wastematerials such as silica sand, Kevlar fibers, fly ash, sludges, slags,waste paper, rice husks, saw dust, and the like, volcanic aggregates,such as expanded perlite, pumice, scoria, obsidian, and the like,minerals, such as diatomaceous earth, mica, borosilicates, clays, metaloxides, metal fluorides, and the like, plant and animal remains, such assea shells, coral, hemp fibers, and the like, manufactured fillers, suchas silica, mineral fibers and mats, chopped or woven fiberglass, metalwools, turnings, shavings, wollastonite, nanoclays, carbon nanotubes,carbon fibers and nanofibers, graphene oxide, or graphite.

It will be appreciated that the descriptions above with respect toparticular embodiments above are not intended to limit the invention inany way, but which are simply to further highlight or illustrate theinvention.

In the foregoing specification, it is to be understood that theinvention is not limited to the exact details of procedures, operation,exact materials, or embodiments shown and described, as modificationsand equivalents will be apparent to one skilled in the art. Accordingly,the specification is to be regarded in an illustrative rather than arestrictive sense. For example, specific combinations of proppantmaterials, coatings, additives, and folding, crumpling, and/or sizereduction processes to form the proppant particles, reaction conditionsto form the proppant particles, hydraulic fracturing method steps, andthe like, falling within the claimed parameters, but not specificallyidentified or tried in a particular method, are anticipated to be withinthe scope of this invention.

The words “comprising” and “comprises” as used throughout the claims areto be interpreted as “including but not limited to” and “includes butnot limited to”, respectively.

The present invention may suitably comprise, consist of or consistessentially of the elements disclosed and may be practiced in theabsence of an element not disclosed. For instance, the proppant mayconsist essentially of or consist of at least one crumpled layer havingouter perimeter defining a proppant volume and at least one intersticewithin the proppant volume adjacent the layer.

There may be further provided a method of making a proppant consistingessentially of or consisting of providing a layer, and then notnecessarily in this order: crumpling the layer and finely dividing thelayer to produce a proppant comprising, consisting essentially of orconsisting of at least one crumpled layer having outer perimeterdefining a proppant volume and at least one interstice within theproppant volume adjacent the layer.

Further there may be further provided a method of fracturing asubterranean formation comprising, consisting essentially of orconsisting of introducing a proppant stage into the subterraneanformation, wherein the proppant stage comprises, consists essentially ofor consists of a carrier fluid and a proppant, where the carrier fluidis selected from the group consisting of brine, slickwater, an aqueousfluid gelled with a linear gel, an aqueous fluid gelled with acrosslinked gel, an aqueous fluid gelled with a viscoelastic surfactant,or delivered with a gas such as carbon dioxide and/or nitrogen, andmixtures thereof; and the proppant comprises, consists essentially of orconsists of at least one crumpled layer having outer perimeter defininga proppant volume and at least one interstice within the proppant volumeadjacent the layer.

What is claimed is:
 1. A proppant comprising: at least one crumpledlayer having outer perimeter defining a proppant volume, the at leastone crumpled layer comprising a material selected from the groupconsisting of ceramic, metal, polymer, and combinations thereof; and atleast one interstice within the proppant volume adjacent the layer; theproppant having: an average particle size of from about 125 to about1700 microns, and a strength of from about 1,000 to about 10,000 psi(about 6.9 to about 69 MPa).
 2. The proppant of claim 1 where: theceramic is selected from the group consisting of aluminosilicate,zirconia, metal carbides; the metal is selected from the groupconsisting of aluminum, titanium; the polymer is selected from the groupconsisting of carboxymethyl cellulose (CMC), polyethylene terephthalate,polyimides, polyethylene, polypropylene, polycarbonate, polyurethane;and combinations thereof.
 3. The proppant of claim 1 where the layer hasa thickness ranging from about 1 mm to about 5 microns.
 4. The proppantof claim 1, where the proppant has a density less than about 2.45 g/cc.5. A proppant comprising: at least one crumpled layer having outerperimeter defining a proppant volume, the at least one crumpled layercomprising a material selected from the group consisting of ceramic,metal, polymer, and combinations thereof, where: the ceramic is selectedfrom the group consisting of aluminosilicate, zirconia, metal carbides;the metal is titanium; the polymer is selected from the group consistingof carboxymethyl cellulose (CMC), polyethylene terephthalate,polyimides, polyethylene, polypropylene, polycarbonate, polyurethane;and combinations thereof; and at least one interstice within theproppant volume adjacent the layer.
 6. The proppant of claim 5 where thelayer has a thickness ranging from about 1 mm to about 5 microns.
 7. Theproppant of claim 5 having an average particle size of from about 125 toabout 1700 microns.
 8. The proppant of claim 5 having a strength of fromabout 1,000 to about 10,000 psi (about 6.9 to about 69 MPa).
 9. Theproppant of claim 5, where the proppant has a density less than about2.45 g/cc.